Prof Paul HO from the Department of Pharmacy in NUS and Prof Shih-Hui LIM of Duke-NUS Graduate Medical School together with their graduate student Dr Sing Teang KONG evaluated the prevalence of epileptic adults with drug resistant epilepsy (DRE) according to the latest definition for DRE as specified by the International League against Epilepsy (ILAE) 2010 consensus. Previously, the varying definitions of “refractory” or “resistant” among studies hindered direct comparisons. The more precise definition of DRE allows unraveling pertinent risk factors in DRE development and correlate patient specific characteristics with seizure outcomes.

557 epileptic adults who had attended the neurology specialist clinic of a tertiary referral hospital in Singapore were profiled for drug responses according to the definition for DRE as specified by the ILAE 2010 consensus (see Figure). This is a retrospective cohort study. Data collected included demographics, characteristics of seizure and epilepsy, blood biochemistry levels, electroencephalogram and brain imaging findings, and medication histories. The types and dosages of antiepileptic drugs (AEDs) used were retrieved from case notes and checked against pharmacy records. Each patient was counselled upon the diagnosis of epilepsy and taught to maintain a seizure diary. The dates and number of seizures were retrieved from these diaries at each visit. Treatment-related adverse effects were routinely assessed and hence, patients were assumed to not have treatment-related adverse effects when no relevant documentation was encountered.

The prevalence rate of DRE in this clinic was 21.5%, while 40.9% of PWE were drug responsive/seizure free at the point prevalence day. From multivariate analysis, patients with structural-metabolic etiology, mental retardation, psychiatric illnesses and pre-treatment seizure frequency of more than once monthly were found to be more likely to have DRE. Although the influence of Indian ethnicity on the risk of DRE was only found in the univariate analysis, it warrants investigation in a larger cohort.

The findings may aid policy makers in designing treatment guidelines and allocating resources for epileptic patients, with careful considerations that at any given time, 1 in 5 epileptic adults have DRE.

Age specific prevalence of drug resistant epilepsy in 557 people with epilepsy attending a neurology specialist clinic in Singapore. Highest DRE prevalence was observed in the 40 – 49 years old group. The subjects in the 60 – 69 years old group had a significantly lower prevalence of DRE as compared to the other age groups.